Piston



J. W. HOWLETT April 9, '1946. l

vPISTON I Filed Oct. 28, 1944 mi Imm 170.3); `y1? az" QL MAW @ig Patented Apr. 9, 1946 PISTON .161m ,izviliiam'y Howlett,

England London, England, 'assigjnor to Wellworthy'Piston Rings Limi-ted, londoxnV Apnlieaten October, 28, 1944, Serial No. 560,842

W In Great Britain MaylZ, 1,944

Claims.l (Cl. 309-11) Thisinventiong, relates to a cast metal piston, fora duid-pressure engine, of the. kind hei/ms intermediate vskirt portions. et; the pressure faces (i. e., at the faces at the ends of a diameter of the piston which is at right-anglestothe axis of the wrist; pin) ,which do not extend circumferentially estar. asthe. wristpin bossesand the lues 'supper-ting the bossesl from theY head, the intermediate skirt portions beine internally connected with the wrist nin bosses, by reiativelyeexibie websv and being directly connected to a. ski-rt portion remote from the head.

Examples of pistons of; this kindv are disclosed in the specicatipns Off` British Patents Nos. 366,625 and 426,190,l and 'in practice; they are very satisfactory. c

In casting a, piston. of; the kind; disclosed in either of these prior specifications, the die has thin wing plugs: which lie; against the outer faces ofv thesaid webs, i. e., between the webs and the internal faces of the intermediate skirt portions; and, assuming thai-.the piston iscgastwith its head downwards, these wing plugs. must be withdrawn vertically after the casting operation. From this it follows that, to allow of the withdrawal of the wing plugs, it is not possible to provide the said skirt portion, which is remote from the head, with an internal belt of material, which belt can subsequently be externally machined to provide a yscraper ring groove.

In some cases, however, it is important that a piston of the kind aforesaid should have a scraper ring mounted in its skirt on the side of the wrist pin bosses remote from the head. It is my main object to provide means whereby this shall be possible. y

It is a further object that the circumferential spaces between the edges and inner faces of the intermediate skirt portions, on the one hand, and between the wrist pin bosses and the lugs supporting these portions, on the other hand, shall be shaped so as to allow plugs deiining the shape of these spaces to be removed, after casting, in the direction of the wrist pin axis.

The piston may have at least one of the intermediate skirt portions severed by a part-circumferential slit from -direet connection with the head. Furthermore, it may have a longitudinal slit extending from the end of the piston remote from the head as far as the part-circumferential slit, i. e., through one of the pressure faces of the piston.

In the accompanying drawing:

Figure 1 is an elevation of a piston according to the invention;

Figure 2 is a central longitudinal section taken on the line IIV-II of Figure 1; l

Figure 3 is a cross-section taken on the line IIIf-III of Figure 2 and Figure 4 is an underneath View of Figure l. In the constructionshown, the piston is formed of a light alloy vas a die casting either by gravity or pressure methods. The head 9" has two piston ring grooves Ii), l0, init andascraper ring grooveV extend c ircumierentially as. far as the wrist pin bosses vI5; andthe lugs litfsupporting them, and the intermediate skrtportions are internally connectedwiththe'wristpin bosses. by means ofv relatively-flexible webs I9, I9. One of the intermediate skirt portions, marked I'la in Figures l, 2 and 3, is severed from the head by a part-circumferf ential slit 20. This pressure face of the skirt has a longitudinal slit 2| in it extending from the slit 2B through the skirt portion 22 remote from the head. In the latter skirt portion, which is formed integrally with the intermediate skirt portions, is left an internal belt of metal 23 which.

is subsequently externally machined to provide a scraper ring groovehaving through openings 24 communicating with the interior of the piston. 25 represents a stop peg mounted in this belt of metal and extending into the groove to prevent the scraper ring from turning. v

In casting this piston it would not be possible to use axially-draw-out wing plugs, as aforesaid, as their withdrawal would be prevented by the b-elt 23. I have therefore arranged the -circumferential spaces 21 (see Figure 3), between the adjacent edges of each intermediate skirt portion and the adjacent edges of the wrist pin' bosses and their supporting lugs, so that they, can be shaped by plugs which, after casting, can be withdrawn laterally, i. e., in the direction of the axis of the wrist pin bosses. The spaces 21 taper slightly in cross-section, as shown by Figure 3, to admit of this. Y

Thus, by means of the invention I obtain a exiblecast piston which has the advantages of the kind aforesaid and which is able, in addition.

to carry a scraper ring in the skirt portion remote from the head. Y Y

What I claim as my invention'and V,desire to "secure by Letters Patent of the United States is: 1. A cast metal piston having a head, wrist pin bosses rigidly supported from the head, intermediate skirt portions, at lthe pressurevfaces, which do not' extend 'circumferentially Vas far v,as` the.'

wrist pin bosses, relatively-nexible webs of generally part-cylindrical shape connecting saidV .Y bosses to the inner faces of said intermediate skirt portions, the circumferential spaces be`-Y tween the edges of said intermediateskirt por.-v y

tions and said bosses being lshaped.V solas,tofallo'wV plugs defining the shape of these spaces to be removed, after casting, in the direction of the wrist pin axis, and a skirt portion, remoterfrom fr the head, connected to said intermediate skirt portions. Y

2. A cast metal piston having a. head, wrist pin bosses, lugs rigidly i supporting, the wrist pin bosses from the head, intermediate skirt portions, at the pressureA faces, which do `not extend circumferentially as far asthe wrist'pin bosses or said lugs, relatively-exible webs of generally part-cylindrical shape connecting said bossesV to the vinner faces of said intermediate skirt por? tions, the circumferential spaces between rthe Y' -edges of said intermediateskirt portions', on the one hand, and saidvbosses andthe lugs supporting these bosses, on Ythe other hand,-being shaped so as to allow plugs deiiningv the shape of these Yspaces to' be removed, after casting'jin the di-` rection of the wrist pin axis`,'and 'a skirt portion, remote from the head, connected to said intermediate skirt portions. v Y Y 3. Ascast metallpistonof light alloy having a head, wrist rpin bosses 'rigidly supported from the head; Vintermediate skirt'portions, at the pres-v sure faces, which'do notextend circumferentially as far as the wristpin bosses, -relatively-iiexible` webs .of generally peut-cylindrical.,shape.l conriecting said bosses to the -inner.facesof Lsaid iny termediate skirt portions, the circumferential spaces between the edges of said intermediate vskirt portions and said bosses being shaped'so as ,to allow plugs defining the shape of these spaces to be removed, after casting, in the direction of thefwrist pin axis, and a skirt portion,

remote frointhe head,,p c,onnetd ,to said inter- ,mediatev skirt fportionsg, said skirt portion, remote from the head, having therein a belt of metal which is peripherally grooved to receive 'a scraper ring. Y

4. A v cast metal piston of light alloy having a head, wrist pin bosses rigidly supported from the head, intermediate skirt portions, at the pressure faces, which do not extend circumferentially as far as the Wrist pin bosses, atleast one -Osaidintermediate skirt portions being severed -byeJ part-circumferential slit from direct connection'with the head, relatively-flexible webs of generally part-cylindrical shape connecting said bosses to the inner faces of said intermediate skirt portions, the circumferential spaces between the edges ef said intermediate sir-iiiV portions and said bosses beingshaped so as to 'allow plugs de-v iining the shape of Athese-spaces to be removed, after casting, 'in the J direction of the :wrist pin axis, and avr skirt portion, remote lfrom the head,

connected to said intermediateskirt portions.

5. A cast metal piston having a head, wrist pin bosses rigidly'supported'from the head, intermediate skirt portions, atthe pressure faces, which do not extend circumferentially 'as far as the wrist pinv bosses, relatively-flexible ywelos of generallyY part-cylindrical shape I connecting said bosses to the inneriaces ofV said yintermediate skirt portions, the circumferential spaces between the edges of saidlintermediate skirt portions and said bosses tapering sofasto-'allow plugs denning the shape of these spaces tolbe removed, after casting, in the direction of the. wrist `pin' axis, and a skirt portion,remotefrom the head, connected to said intermediate skirt portions. J

Y JJOHN5W]1LIAMLHOWLETT. 

